Deep brain stimulation may be used to treat a number of neurological and psychiatric disorders. For treatment in patients with Parkinsons' disease it is necessary to place the electrode precisely within the center of the target nucleus. Precise electrode placement provides optimal therapeutic results while minimizing possible side effects. Currently, the final coordinates for the electrode is determined by electrophysiological mapping. It is a slow, painstaking process not without potential complications. We propose to develop and evaluate two procedures to compliment current microelectrode mapping procedure. A fiberoptic-based probe will be employed to optically map the boundaries of the STN and GPi using only a single electrode tract. We also propose to develop a method to detect blood vessel using fiber sensors as part of the microelectrode assembly. Besides a role in the treatment of Parkinson's disease, the methods to be developed may be applied to stereotactic brain procedures for other neurological and psychiatric disorders. For example, it could be used to more precisely guide the biopsy of deep seated brain lesions. It could be used to more safely guide the placement of depth electrode for the diagnosis and treatment of refractory seizures. And optically guided stimulating electrodes may someday be used to treat depression and other psychological disorders.